A rating score of ultrasonography to evaluate the pathological severity and timing of operative intervention of acute cholecystitis was designed. The ultrasonic rating score consisted of 7 items with were sensitive and specific in diagnosis of acute cholecystitis, accorded with the findings during operation. Emergency cholecystomies performed on patients with score < or = 10, 11-18 and > 18 points were 1/30, 4/42 and 7/13 respectively, followed by definite procedures. The results suggest that the ultrasonographic rating score is an useful approach in ultrasound diagnoses and timing of operation for acute cholecystitis.